I used Airlok Extra bags lashed both front and rear before I got my Wildcat harnesses.
Just strapped on with 2 straps front, 3 straps rear (and a bit of double-sided velcro around the seatpost). I was happy with them for short trips. Stability was pretty good at the front. Acceptable at the rear. Items in the rear tended to settle off-road and create slack in the straps in places, meaning a quick re-tighten.
For longer trips I would have got the sewing machine out and made a bit of a sling for the rear, but the Wildcat Tiger arrived in time to mean I didn’t have to do that 🙂
However, I did manage to bodge the old rear so that it would work with the Joplin seatpost. Now I’ve got the Wildcat and a longer-travel Reverb, I haven’t been able to make it work.
The most important difference between the lashing and Wildcat solutions is that one made me check it every gate/stop, and also constantly leave me thinking I could do a slightly better job, whereas the other leaves me relaxed.